Gears, bearings, camshafts, planet shafts, and other engine, transmission, and/or undercarriage components in a machine, such as an earthworking machine, are constantly subjected to rolling and/or sliding contacts. Track links, track rollers, bushings, idlers and ground engaging tools (GETs) are generally also subjected to abrasive wear and/or bending forces. In order to increase the durability and reliability of the components that experience such contacts, these metallic components are usually case hardened. Case hardening results in the component having a harder outer surface and a relatively softer inner core and is accomplished by methods such as carburizing, induction hardening, flame hardening, or other selective hardening processes known to those skilled in the art of heat treatment.
One disadvantage of case hardening by these case hardening processes is that hardness gradients are introduced through a differential gradient of martensitic and non-martensitic structures that is independent of the elastic modulus of the component. Thus, even though the outer surface of the component may have a greater hardness than the inner core and consequently have better wear resistance, if the loads or stresses are kept constant, the deflection or strains of the component is unchanged. In other words, the component still undergoes a constant amount of deflection at a constant load. This inability to tailor a component's deflection at greater loads has long been a bottleneck in the design of various types of components that are subjected to a variety of contacts enumerated above. It has been desirable to have components subjected to rolling and/or sliding load conditions that are designed to exhibit varying amounts of Von Mises stresses in response to a constant amount of deflection. In other words, it has been desirable to have components which are tailored to exhibit varying amounts of deflection at a fixed amount of load, thus tailoring the bending or contact fatigue resistance or wear resistance of the component according to its intended application in a machine. It has thus been desirable to have components having an elastic modulus profile in relationship to the depth from the surface of the component, and also in relationship to the geometrical configuration of the component, so as to obtain components that exhibit a desired amount of fatigue or wear resistance enhancement when subjected to one or more of rolling, sliding, abrasion or bending contacts.
The present invention is directed to overcome one or more problems of heretofore utilized components that are subjected to one or more of rolling, sliding, abrasion, or bending contacts.